1. Field of the Invention
The present invention relates to a charged particle beam lithography apparatus and method which can form a charged particle beam emitted from an electron gun in a desired beam shape and performs lithography by irradiating the charged particle beam on a test piece.
2. Description of the Related Art
FIG. 9 shows a configuration view of a charged particle beam lithography apparatus according to a related art. (e.g., see JP-A-9-63937) On an advancing path (that is, on one optical axis) of a charged particle beam emitted from an electron gun 1, a charged particle beam forming portion, that is, a first illumination lens 4, a beam limitation aperture 5, which is provided so that the center thereof corresponds to the center of the first illumination lens, a second illumination lens 7 and a first forming aperture 16 are arranged, and further downstream, a first projection lens, a forming deflector, a second projection lens, a second forming aperture, a reduced lens and an objective lens and the like are arranged. The charged particle beam is formed by the charged particle beam forming portion to be irradiated on a test piece.
A first alignment deflector 2 is provided between the electron gun 1 and the first illumination lens 4. A third alignment deflector 6 is provided between the first illumination lens 4 and the second illumination lens 7. Further, at the downstream of the second illumination lens 7, a fourth alignment deflector 8, a blanking deflector upper pole aperture (a first blanking aperture) 9, a blanking deflector upper pole 10, a blanking aperture (a second blanking aperture) 12, a fifth alignment deflector 13, a blanking deflector lower pole 14, a sixth alignment deflector 15 and a first forming aperture 16 are provided in this order.
According to such a configuration, the charged particle beam emitted from the electron gun 1, that is, a crossover image is formed five times by the first illumination lens 4, the second illumination lens 7, the first projection lens, the second projection lens and the reduced lens, and finally, is formed on a main surface of the objective lens. In addition, the charged particle beam emitted from the electron gun 1 passes through the first forming aperture 16, and then is deflected by the forming deflector to pass through the second forming aperture. Thus, the charged particle beam is formed in an aperture shape which combines the first forming aperture with the second forming aperture. Thereafter, the formed charged particle beam is imaged on a surface of the test piece by the reduced lens and the objective lens.
In the upstream of the charged particle beam lithography apparatus as such a configuration, the center of the beam limitation aperture 5 in the first illumination lens 4 has been referenced, the first alignment deflector 2 has been controlled so that the beam emitted from the electron gun 1 passes through the center.
On the other hand, the charged particle beam lithography apparatus is configured in such a way that from the electron gun 1 to a position, where the first forming aperture 16 is fixed, is divided into seven blocks and outer cylinders corresponding to the respective blocks are stacked. The blocks 1 to 7 respectively mainly include a part (parts) as described below.                Block 1 (17): electron gun 1        Block 2 (18): chamber housing electron gun 1        Block 3 (19): first alignment deflector 2, first illumination lens 4, beam limitation aperture 5 and third alignment deflector 6        Block 4 (20): outer cylinder connecting block 3 with block 5        Block 5 (21): second illumination lens 7, fourth alignment deflector 8        Block 6 (22): blanking deflector upper pole aperture 9, blanking electrode upper pole 10, blanking aperture 12, fifth alignment deflector 13, blanking deflector lower pole 14 and sixth alignment deflector 15        Block 7 (23): first forming aperture 16        
Outer cylinders of these blocks are designed with precision of tens μm of tolerance, reference of a radius direction between blocks becomes a fitting portion of the outer cylinder. Pole pieces, deflectors and apertures are fixedly positioned via a plurality of components based on these blocks.
In such a device, once blocks located downstream from the block 1 (17) are assembled, it is needless to disassemble them as long as a breakdown is not found, therefore, the blocks are assembled with high tolerance.
However, because the electron gun 1 is a consumable, after it is used for a certain period, it is exchanged for another electron gun. Therefore, it is required that the block 1 (17), in which the electron gun 1 is arranged, is configured so as to be easily opened/shut, and it is difficult to make the precision of assembling tighter in comparison with the other blocks. Further, it is difficult to improve the precision of a position and direction of the beam emitted from the electron gun 1. In such circumstances, a condition, where the emitting position or emitting direction of the beam emitted from the electron gun 1 is likely to deviate from the center axis of the device, unavoidably occurs.
In such a case, even though the first alignment deflector 1 is controlled so that the beam emitted from the electron gun 1 passes through the center of the beam limitation aperture 5 in the first illumination lens 4, as shown in FIG. 9, the axis deviation at the upstream of the device reoccurs at the downstream, the beam approaches the structures located downstream, the possibility that the beam is shielded increases, therefore, there remains a problem such that a beam defect or a beam blur is likely to arise and precise lithography cannot be performed.